1. Field of the Invention
This invention relates to musical tone control apparatuses using piezoelectric sensors and sensing devices having pressure sensibility used for electronic musical instruments.
This application is based on Patent Application No. Hei 10-184437 and Patent Application No. Hei 10-217146 both filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
Conventionally, there are provided a variety of technologies for musical tone controls using pressure sensitivity. For example, the paper of U.S. Pat. No. 4,043,241 (which corresponds to Japanese Patent Publication No. Sho 54-19338) discloses a musical shoe, i.e., a shoe-type musical instrument that generates musical tones in response to motion of a foot or leg of a human operator (or performer). Herein, electronic circuits and a speaker are stored inside of a case body having a ship-like shape. In addition, multiple switches are arranged on a lower side surface of the case in connection with names of musical tones respectively. The performer puts the case body on his or her foot. So, the performer is capable of playing melody sounds by turning on the switches with his or her foot steps.
The aforementioned shoe-type musical instrument is conventionally designed to have a capability of merely changing over the names of the musical tones to be produced. There is provided another conventional technology which performs musical tone controls in response to foot motions, which is designed for the system of electronic musical instruments which are generally capable of performing the musical tone controls with respect to multiple music elements such as tone volumes and tone colors. For example, the paper of U.S. Pat. No. 5,714,706 (which corresponds to Japanese Patent Application, Publication No. Hei 9-68973) discloses a musical tone control apparatus using a foot sensor of a shoe insole type, which is equipped with piezoelectric sensors. Herein, the musical tone control apparatus controls musical tones by detecting pressures that a performer applies to the piezoelectric sensors with a toe and a heel respectively.
In addition, some musical tone control apparatuses are designed like percussion instruments by employing pad units that are beaten by sticks or else. Herein, the pad unit is constructed using a sensing unit which is coupled to a pad skin to be beaten and which has a sensitivity in sensing beats applied to the pad skin. So, the musical tone control apparatus generates musical tone control signals in response to outputs of the sensing unit. For example, the paper of Japanese Patent Application, Publication No. Hei 9-297576 discloses an electronic drum device which is an example of the aforementioned musical tone control apparatus. In addition, the paper of Japanese Patent Application, Publication No. Hei 6-175651 discloses an electronic drum, wherein a piezoelectric sensor is securely attached to a pad plate that is fit into a pad rubber (i.e., pad skin). Herein, the pad plate is connected together with a base plate at the periphery thereof by means of cushion members. Thus, the piezoelectric sensor detects vibrations of the pad plate which vibrates when the pad rubber is beaten.
By the way, the conventional musical tone control apparatus of the shoe type employs a sensor unit which is shown in FIG. 11A and FIG. 11B. Such a sensor unit suffers from a problem as follows:
A piezoelectric sensor "a" is securely attached to a displacement disc face plate "b", which is arranged to face with a reference disc face plate "c" via a spacer "d". Herein, the reference disc face plate c is brought into contact with a contact surface of a shoe that a sole of a foot of a person comes in contact with. The spacer d is formed with regard to a part of an area by which the displacement disc face plate b faces with the reference disc face plate c. That is, the sensor unit has a structure in which the displacement disc face plate b is subjected to cantilever support. For this reason, the sensor unit has specificity in a direction that external force is applied. In a situation where force is selectively applied to the spacer d, a dead zone (or insensitive area) occurs around the spacer d. Therefore, an output level of the sensor unit differs in response to a direction and a position to step a foot, regardless of an amount of force to step a foot. Namely, the conventional musical tone control apparatus of the shoe type has somewhat a peculiarity in sensing the pressure that the performer's foot applies to the sensor unit.
In addition, the conventional musical tone control apparatus employs an insole-type foot sensor, so it suffers from a problem as follows:
Suppose a situation that the performer steps his or her foot constantly to operate the foot sensor at a portion where the performer intends to touch with a sole of the foot. In such a situation, however, a position of a toe and a position of a heel are slightly shifted from intended positions on the piezoelectric sensor in response to an angle and a direction to step the foot. For this reason, the conventional apparatus must perform "unintended" musical tone control. In other words, the conventional apparatus lacks fidelity as an input device (or input interface) of the foot motion.